Conventionally, aircraft runways are identified by having boundaries which are identified by runway lights. These runway lights are conventionally incandescent bulbs encased in a weatherproof fixture. The Federal Aviation Administration (FAA) is considering replacing standard runway lights with high intensity light emitting diode (LED) runway lights. There are a number of reasons, including cost savings, that are compelling for the FAA to make such a change. The change would likely be phased, occurring over a seven year time frame in the absence of other drivers. If additional airport capacity could be shown, the time frame may be moved up. An additional component that the FAA may consider is for the LED lights to be modulated (for example through pulse coding) so that they can be detected at greater ranges by electronic imaging systems and to make them very distinct from all other light sources to ensure that the correct runway lights are detected. Different runways may be coded differently so that aircraft crew members could ensure that they were landing on the correct runway, on 16L and not 16R, for example. With coded light the LED's may potentially be detected electronically in today's equivalent of a 300-foot runway visual range (RVR) fog at Portland or SEATAC, for example. This would provide a substantially 100% landing capability and could even allow a head-up-display-monitored automatic landing even at WAAS or CAT I ILS facilities.
An imaging sensor with a sufficiently high frame rate may permit the pulse coding of the individual LED's to be detected and decoded, effectively implementing a matched filter for the LED modulation patterns. This would improve the ability of the imaging sensor to reliably detect and identify the runway lights in the presence of obscurants like fog. The end result could be a clean image of only the airport lights that can be presented on the head-up display (HUD) and head-down display (HDD). Computer analysis of the geometry of the runway lights in this image can provide independent verification of the position and attitude of the aircraft with respect to the runway. This additional independent information can be used to certify a landing system based on GPS or ILS to operate safely in lower visibility conditions than would otherwise be possible.
In addition to runway lighting, airports are conventionally provided with similar lights along either side of each taxi way to facilitate movement of aircraft between the runways and the terminal area. These lights are conventionally colored differently (blue) from runway lights (red) and are not as bright. As there are often many taxiways with correspondingly many intersections, it can be difficult for pilots to maintain an awareness of their position on the airport surface, particularly at night. The same modulation techniques that facilitate location and identification of the correct runway described above could also be applied to the taxi-way lighting system.
While the above description addresses the application of LED runway lights in a civil environment, military runways differ in that where the civil runway should be clearly visible to all aircraft in its vicinity, it may be desired that the military runway be easily visible only to friendly aircraft. A military runway or landing zone that is difficult for the enemy to see is correspondingly difficult to attack.
The techniques herein below extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.